Complete coding sequences and haplotypic associations of HLA-B*0707, -B*1524, -B*4405, -B*4802, -DRB1*0409, -DRB1*0411, -DRB1*1115, -DRB1*1305, and the novel allele -DRB1*0709. Group-specific amplification of cDNA from DRB1 alleles associated to DRB3 and DRB4

HLA class II peptide-binding-region analysis reveals funneling of polymorphism in action

BACKGROUND

HLA-class II proteins hold important roles in key physiological processes. The purpose of this study was to compile all class II alleles reported in human population and investigate patterns in pocket variants and their combinations, focusing on the peptide-binding region (PBR).

METHODS

For this purpose, all protein sequences of DPA1, DQA1, DPB1, DQB1 and DRB1 were selected and filtered, in order to have full PBR sequences. Proportional representation was used for pocket variants while population data were also used.

RESULTS

All pocket variants and PBR sequences were retrieved and analyzed based on the preference of amino acids and their properties in all pocket positions. The observed number of pocket variants combinations was much lower than the possible inferred, suggesting that PBR formation is under strict funneling. Also, although class II proteins are very polymorphic, in the majority of the reported alleles in all populations, a significantly less polymorphic pocket core was found.

CONCLUSIONS

Pocket variability of five HLA class II proteins was studied revealing favorable properties of each protein. The actual PBR sequences of HLA class II proteins appear to be governed by restrictions that lead to the establishment of only a fraction of the possible combinations and the polymorphism recorded is the result of intense funneling based on function.

Analysis of the complete cDNA sequences of HLA-DRB1 alleles with group-specific amplification primers in the Chinese Han population

Currently for the majority of HLA-DRB1 alleles the focus has been mainly on exon 2 and complete cDNA sequences of HLA-DRB1 alleles are rare. In this study, we analyzed the complete coding sequences of partial alleles of HLA-DRB1 locus. The cDNA was amplified by polymerase chain reaction using the group-specific primers located in the 5'- and 3'-untranslated regions to obtain the complete coding sequences. The amplification products were sequenced using an ABI BigDye® Terminator Cycle Sequencing kit. The HLA-DRB1 allele phylogenetic tree was analyzed by dnaman software. Full-length cDNA sequences of 22 HLA-DRB1 alleles were obtained in this study. HLA-DRB1*08:09, DRB1 *12:02:01, and DRB1*13:12 alleles were first reported for complete coding sequences. The sequences of exon 1 of HLA-DRB1*04:06:01, DRB1*08:03:02, and DRB1 *14:07:01 were newly presented. The complete coding sequences of HLA-DRB1 *01:01:01, DRB1*03:01:01:01, DRB1*04:01:01, DRB1*04:05:01, DRB1*07:01:01: 01, DRB1*09:01:02, DRB1*10:01:01, DRB1*11:01:01, DRB1*12:01:01, DRB1*13: 01:01, DRB1*13:02:01, DRB1*14:04, DRB1*14:54, DRB1*15:01:01:01, DRB1*15: 02:01, and DRB1*16:02:01 were identical to those previously reported. Forty polymorphic positions in complete coding sequences outside exon 2 of these HLA-DRB1 alleles were confirmed. According to the phylogenetic tree of full-length coding sequence, the HLA-DRB1 allele was classified into seven major allelic lineages. In conclusion, a protocol for HLA-DRB1 cDNA amplification and sequencing was improved and the data may help to determine the polymorphism of coding sequences outside exon 2.

HLA-B*0777 allele differs from B*0707 by a single residue in the antigen binding groove

Human leukocyte antigen (HLA) class I sequence-based typing (SBT) for hematopoietic unrelated donor searching in a Romanian Caucasian patient showed the presence of a novel HLA-B allele defined as B*0777. HLA-B*0777 has two nucleotides changes at the same codon from B*0707, resulting an amino acid replacement 99Y > 99S.

Group-specific amplification of cDNA from DRB1 genes. Complete coding sequences of partially defined alleles and identification of the new alleles DRB1*040602, DRB1*111102, DRB1*080103, and DRB1*0113

We present here the complete coding sequences, previously unavailable, of the DRB1 alleles DRB1*030102, *0306, *040701, *0408, *1327, *1356, *1411, *1446, *1503, *1504, *0806, *0813, and *0818. For cDNA isolation, new group-specific primers located at the 5'UT and 3'UT regions were used to carry out allele-specific amplification and a convenient method for determining full-length sequences for DRB1 alleles. Complete coding sequencing of samples previously typed as DRB1*0406, DRB1*080101, and DRB1*1111 revealed new alleles with noncoding nucleotide changes at exons 1 and 3. In addition, we found a novel allele, DRB1*0113, whose second exon carries a sequence motif characteristic of DRB1*07 alleles. The predicted class II haplotypic associations of all alleles are reported and discussed.